This is a type of plot that illustrates how data are distributed around the central, or median, value. The ‘box’ generally represents the range of the central 50% of values around the median which is shown as the line through the box. Values that are further from the median are illustrated by whiskers, outliers or extreme values, depending on how far the value is from the median and on the size of the range between the quartiles. For example, if only one data value has been collected, then the value appears as a single line (i.e., as the median value) and there are no whiskers, outliers or extreme values.